mills



o. L. MILLS ELECTRIC ARC FURNACE Original Filed March 5. 1929 2 Sham-Sheet 1 F 1: Z Flt. l

Feb. 3, 1 2.1.

INVENTOR ,0; 0/1.. M BY M ATTORNEY O. L. MILLS ELECTRIC ARC FURNACE Feb. 3, 1931.

Re. 17,954 2 Sheets-Sheet 2 Original Filed March 5, 1929 R isaued Feb. 3, 1931 UNITED s'ra'ras I as. time PATENT OFFICE-1i? OSCAR L. KILLS, OF LOS ANGELES, CALIFORNIA, ASSIGNOR '10 HILLS ALLOYS INC" 01 LOS ANGELES, CALIFORNIA, A CORPORATION Q1 DELAWARE morale-sac seamen Driginal Ko.'1,719,558, dated This application is a continuation in part of my prior application, Serial No. 331,747, filed January 1.1., 1929, and entitled Process and apparatus for making tungsten alloys. It is one of the objects of my invention to provide a furnace utilizing the electric are for melting substances, and especially to make 'it possible to secure a working temperature neighboring 6000 F. Such a temperature is required for example, to melt tungsten, and to cause it to combine chemically with carbon to form thetungsten carbides. These materials are useful in connection with cutting or drilling tools (such as oil well drill bits) because of their extreme hardness. One rocess for manufacturing this materia is claimed and described in my prior application hereinbefore identified, and my urnace is especiall useful for carrying out that process. owever, it can obviously be. applied wherever an extremely high temperature is required, especially at localized spots.

I attain these high temperatures by a novel furnace structure that 'efl'ectively conserves the heat created by'an electric are between electrodes, or between an'electrode and thematerial being treated. I utilize not only the heat directly centered upon the material, but also reflected heat from the roof or ceiling of the furnace.

My invention is, especially adapted for the eflicient' production of tungsten carbide, where Hick, uniform, and intense'heat is r aired to produce a high grade roduct.

y invention possesses many er advantages, and has other objects which may he made more easily a parent from a consideration of one enibo iment of my invention.

For this purpose I have shown a form in thedrawings accompanying and forming part of the present specification. I shall now roceed to describe. this form in detail, w ich illustrates the general principles of my invention; but it is to be understood that this limitin' sense, since the scope of my invention is t defined by the appended claims. Referring tolthe drawings:

\ Figurel is a side elevation embodyin'gmy invention;

detailed description is not to be-taken in aof a furnace J'uly 2, 1929, Serial Ho. 344,494, filed larch 5, 1929. Application tor reissue filed September 30, 1930; S'erial No. 485,540.

Fig. 2 is a longitudinal section thereof; Fig. 3 is'a sectional View, taken along plane of Fig. 1; Fig. 4 is a sectional view, taken along plane 4-4 of Fig. 1;

Fig. 5 is a rear view of a. part of the furnace';

Fig. 6 is an elevation of a half-mold into which the material to be treated can be the straps and one'of the elements 11,12 soas to prevent short-circuting between these ti le' layer, as shown most clearly in Fig. 2.

e outermost layer 15 can be made up of a layer of good heat insulation, not necessarily highly refractory; such as silocell bricks, which are made from diatomaceous earth.

The second layer 16 can built up 'from' vitreous brick; and the innermost layer 17 should be made fromhighly refractory material, such as carbofra'x brick. I have shown these layers 15, 16, 17 ina digrammatic fashion; it is to be understood however that these layers are deposited brick by brick in container 11 and finally covered over by th cover 12. v

These la ers form a comparatively small or confine furnace chamber 18 heving an openingli) whereby the operation can viewed by an attendant. I refer to utilize carbon electrodes between w ich anarc can form inside of the chamber 18 Thus there through an a rture in the bottom of base 111, and over it is disposeda thick layer or floor 21 .of carbon dust or particles or both.

parts. I .75 The walls of the furnace are built in a mul- .is a lower electrode 20 of carbon, projecting ly beyond the outer member 25, whereby an annu ar shoulder or surface 26 isformed,v surrounding core 24 ands aced above. its lower end. The are is inten ed to be formed between the lower end of core 24 and material placed in contact with layer 21, and which is to be subjected to the heat of the are, This material 27 is in powdered or anular form, as indicated in my prior app 'cation, can be held in a carbon container 28. This container is shallow so as to ensure uniform heating from the arc, the depth of thespace causes it efiectively to act as a surface. A further separation correspondtherein bein no greater than about threefourths of the diameter, or of the average width, of this space. The circuit is completed betweenelectrode 24 and electrode 20 through 21, container 28, material 27 and the arc itself.

Persons skilled in the art-of course understand thatsurface 26 is not maintained asahorizontal surface after some operation of the furnace. Instead, the lowerportion of member 25 wears to some extent, making surface 26 conical.

I find that-an arc voltage of between .30 and 40 volts is best; as it permits the surface 26 as well as the end of\core, 24 to be ke t very close to the material 27 and there y heat reflecting ing to larger ,arc voltages, would tend to reduce the effectiveness of these surfaces, as well as to splash the workfrom the container and to form an arc to the wallsof the furnace.

The entire furnace can besupported on a framework 29. The n per electrode structure 23 is arranged to axially movable so .as to adjust the arc length. For this urpose, and electrode holder 30 is proyided Figs. 1,'

2, and 3). It is formed as a split ring, with a tightening bolt 31 to clam it tightly on rod 25. It can be'water coole as by the pro-. vision of the water jacket 32, the inlet and outlet being generally indicated'at 33 and 34. Bolt 31 also serves to connect a conductor 35 to the holder ring 30 so as to lead current to the structure 23. I I

The holder 30 is provided with spaced extensions 36, which have straps 37, 38 (Figs. 2 and 5) connecting them at the top and bottom surfaces. These extensions thus form a guide for a rack 39. A pinion 40 is supported 1n the space between projections 36 and ulation of handle 43, the re imu meshes with the rack 39. His apparent that rotation of this pinion will cause the holder 30 tomove up and down, and consequently the electrode structure 23 ismoved up and I down. I

Pinion 40 for this urpose is fast on a shaft 41, 'ournaled in pro ections 36. This shaft,

ed on top of the furnace cover 12. For this purpose it is provided with a foot 44 throu h which extend one or more guide pins or bo ts 45. These bolts are fastened to the to of the furnace, and serve to permit a sli ht reedom of motion to the structure 23. 'owever, a spring 46 surrounds each bolt and exerts a pressure to maintain the foot 44 pressed against the cover 12. By ap ropriate manipc 39 can be tilted against the pressure of these springs, on any 0 the edges of foot 44, so as to adjust the position of the are on the material 27. In order to facilitatethis adjustment, a counter-weight 47 can be used on an arm 48.

When pinion 40 is rotated to adjust the position of electrode structure 23, this ad- Justment can be maintained as by the aid of a spring finger 49 (Fig. 5) acting on a friction wheel 50 fastened to shaft 41.

The lower electrode 20 is clamped into a holder 51 that is entirel similar to the holder 30. This holder 51 can-be fastened in any appropriate manner to the furnace structure.

When tungsten carbide is to be made, by the aid of this urnace, the mixture of. metallic tungsten, tungsten oxide, and carbon, as disclosed in my prior application, is'placed in or container 28 and it is placed in the furnace. The operator then strikes the arc and throu h opening 19 observes its action on material 28. By experiencehe can manipulate handle 43 to keep the are moving over the surface of the material 27. As soon as the operator sees that the material-becomes fluid, he pours it into a relatively cool mold, such as shown in Fi s. 6 and 7.

In these figures, t e mold is shown as made of twosemicylindrical halves 52, 53, made from carbon.' The space 54 provides a cool mold to form relativel thinplates of the carbide. Carbon is use ul for the mold material because it can withstand hi h temperatures. Thematerial must be quic y oured in order to secure thev benefits of quic chill-.

ing.

As the electrode surfaces on structure 23 wear or are disintegrated, the inner coreor electrode proper 24 can be urged downwardly as b a mallet, so as to keep the vertical spac- 1ng tween its active end and the annulus 26 ion 40 as desired.

40 arcing portion during operation closely heat to the wor V wears. c5. '5. In an arc at the correct or best value. The entire assembIy-23' of course'can be lowered by pin- The surface 26 and the active arcing surface forms virtually the roof of thefu'rnace. Since it isa carbon surface, it can withstand enormously high temperatures. The electrode structure'23 being greater in diameter than the work 27 in the container 28' tends to keep heat rays away from the top of the fur nace, and cause it'to be reflected generally downward. A solid electrode structure could also be used.

In the present instance, the use of carbon for the electrode structures is needed for providing an atmosphere of carbon bearing gases in the furnace, whereby the format on of tungsten carbide isfacilitated. However, the urnace as described can obviously be used for other processes where an extremely high temperature is required.

-Iclaim:

1. In an arc furnace, means, forming an arc chamber, an electrode structure extending into the chamber, and a work holding container below the electrode structure so as to cause the arc to play on the work, said electrode structure being substantially larger in size than the container so as to cover said work and thereby to assist in confining the heat *to the-work.

2. In an arc furnace, means forming an arc chamber, an electrode structure extending into the chamber, said electrode structure having an active arcing portion, a work hold ing container below the electrode structure, the active arcing portion thereof covering the work in the container substantially entirely, and means for maintaining the active above the container, said electrode structure being -mounted for lateral adjustment,

3. In an arc furnace, means forming an arc chamber, an electrodestructure extend- 7 ing into the chamber, and a work holding container below the electrode structtire so as to cause the arc to play on the work, said electrode structure being substantially larger in size than the container so as to cover-"said {is extendin into the chamber, having an exterior tu ular part and an interior core part slidable in the-exterior part, the end of the 1 interior core part forming an arcing surface f -fsgaced from an annular surface defining an t e end of the thbular part, whereby the core part may b'eadjusted to space the active surfacefro'm the annular-surface at the most favorable distance .as the active surface furnace,a pair of spaced electrodes, one of said electrodes being composed substantially 'entirel of carbon, said electrodes being movab c with respect to each other, means forming a confined arc chamber provided with an opening at the top, '--one of said electrodes bein 'bottomof said chamber, an a work holding container coopcratin with the lower elec: trode, said carbon elb'ctrode extending into said chamber, saidcarbon electrode having a projection on its lower face where the arc is L formed and defining a heat'reflecting annular surface above the lower face of said elec ;v

trode for confiningsome ofthe heat" rays between the two electrodes, said projection being of substantially the same area assaid work holding container.

6. In an .arc furnace, means are chamber, an electrode structure extending into the chamber, said electrode structure having an active arcing portion, and a work holding container below the electrode structure, the active arcing rtion thereof covering the work substantluil y entirely,

as compared with its width. 7. In anarc furnace, means forming an arc chamber, an electrode structure extend located in the forming an the I work container having a depth that is small ing into the chamber, said electrode structure having an active arcing portion, and a work holding container below the electrode structure, the active arcmg portion thereof coveringthe work substantially entirely, the

work container having-an average inside depth not greater than three-fourths of the average inside width.

8. In an arc furnace, means forming an arc chamber, an electrode structure extend- I ing into the chamber, said electrode structure havin an active arcing portion, an open work olding container below the electrode structure, the active arcing ortion thereof entirely, and" covering the work substantia a. thick layer of carbon partic es in vthe bottom of the chamber on which the workcon .tainer is disposed.

9. In an arcfurnace, trodes, one of said electr. es being composed tgair of'spaced elec- 4 substantially entirely of carbon, said elec- ,work and thereb to assist in confining thetrodes bein relativelymovable with respectk, to each ot er, and means forming an arc chamber, the chamber having an openin of substantiall the same area as the area .0 thechamber, said carbon electrode extending into the chamber and having an overallcross section area substantially the sameas that ofthei opening, and said c'arbonelectrodelhavinga proj ection at its end of smaller cross section area, defimn a-substantial heat reflecting.

with respect. to: each 7 other, means forming an arc chamber provided with an opening at the top of substantially the same area as said chamber, one of said electrodes being located in the bottomot saidc-hamber, and a work holding container cooperating with the lower electrode, sa1d carbon electrode extending into saidchamber face of said electrode for confining substan tially all the heat rays bet-ween the two electrodes,

trodes, said projection being of substantially the same area as said work holding container.

11. In an arc furnace, a-pair of spaced elec one of said electrodes being composed substantially entirely of carbon, said electrodes being movable with respect to each other, means forming an arc chamber 'pro vided with an openingat' the top of substantially the same area as said chamber, one of said electrodes being located in the bottom of said chamber, and a work holding container cooperating with the lower electrode, said carbon electrode extending into said chamber and having a cross section area substantially that of said top opening, said carbon electrode having a projection on its lower face where the arc is formed and defining a heat reflecting annular surface above the lower face of said electrode for confining substantiall all the heat rays between the two electro es, said projection being of sub: stantially the same area as said work holding container, said carbon electrode being mounted for lateral adjustment to make the are play uniformly on the work. I a 12. In an arc furnace, a pair of spaced electrodes, one of said electrodes being composed substantially entirely of carbon, said electrodes being relatively movable with respect to each other, and means forming an arc chamber, the chamber having an opening of substantially the same area as the area of the chamber, said carbon electrode extending into the chamber and having an overall cross section area substantially the same asthat of stantially entirely of the opening, and said carbon electrode having a projection at its end of smaller cross section area, defining a substantial heat reflecting annular surface confining substantially all the heat rays between the twoelectrodes, said carbon electrode being mounted for lateral adjustment to make the arc play 'uni formly on the work. I

'13. In an arc furnace, means forming an' arc chamber, said chamber having an opening of substantially the same area as the area of the chamber, and a ir of spaced electrodes one of said. clectr esbeing composed subcarbon and movable through the opening relatively to the other, said carbon'electrode having an overall cross section area substantially the same as that of the opening and said'carbon elect-rode having tainer below the electrode structure so as to cause the arc to play on the work, said containcr having a. depth that is small as compart forming an arcing surpared with its width, said electrode structure being substantially larger in size than the container so as to cover said work and thereby to assist in confining the heat to the work,

In testimony whereof, I have hereunto set my hand. c

OSCAR L. MILLS.

means forming an 7 an electrode structure extending into the chamber, and a work holding con- 

